Rock crystal, mother-of-pearl, onyx and diamond &#x27;Model A&#x27; Mystery Clock, Cartier, 1927 The millegrain-set diamond hands set within a gold frame and a chapter ring applied with mother-of-pearl, rose diamonds and raised gold Roman numerals, the bevelled rock crystal case on a onyx rectangular base, measuring approximately 141 x 90 x 52mm, unsigned, numbered, French assay mark, fitted case and charge key.